Migraine is one of the most common neurological conditions. Migraine headaches affect a large portion of the U.S. population and are more prevalent than diabetes, epilepsy and asthma combined. Migraine is more than just a headache. It can be a debilitating condition which has a considerable impact on the quality of life of sufferers and their families. Attacks can be completely disabling, forcing the sufferer to abandon everyday activities. Even in symptom-free periods, sufferers may live in fear of the next attack. Migraine attacks normally last between 4 and 72 hours and sufferers are usually symptom free between attacks.
Migraine is believed to be caused by the release of a chemical called serotonin or 5HT into the bloodstream. This causes the pain neurons in the blood vessel wall to become irritated. Exactly what causes the release of serotonin is still a subject for research and debate. However, certain factors have been identified which can trigger attacks in susceptible people. Some of these are stress or sometimes the relief of stress, lack of food or infrequent meals, foods containing ingredients such as mono-sodium glutamate, caffeine and chocolate, or alcohol (especially red wine), overtiredness (physical or mental), changes in sleep patterns (e.g., late nights or a weekend lie-in), or hormonal factors (e.g., monthly periods, the contraceptive pill or hormonal changes in males and females as they age).
Migraines are more common than cluster headaches, and have been studied more extensively. In addition, a better and more effective set of drugs have been developed to treat migraines, than cluster headache. For those reasons, the discussion below focuses mainly on migraines, rather than cluster headaches.
“Cluster headaches” were given that name because they tend to occur in episodic clusters, with a cluster cycle usually lasting 4 to 8 weeks. In some patients, a cluster occurs only once in a lifetime; in other patients, a cluster may occur roughly once a year, pith periods of complete remission between attacks; and, in the roughly to % of patients who are chronic sufferers, there are no significant periods of remission. As opposed to migraines (which occur in women at roughly 3 times the rates as in men), cluster headaches are more prevalent in men than in women, by a factor of about 5:1 or higher.
Migraines and cluster headaches are both classified as “recurrent primary headaches”. They are recurrent, since they recur with sufficient frequency to seriously interfere with the health and quality of life of a patient, to a point of requiring and demanding medical attention, as opposed to just taking aspirin or similar over-the-counter analgesics and lying down till it passes. They are also regarded as “primary” headaches, since they usually arise as a primary adverse biologic condition, independently of other causative medical conditions such as tumors, sinus or other infections, bleeding problems, etc.
Current methods for administering anti-migraine pharmaceuticals have major limitations. For example, due to degradation in the gastrointestinal track and low adsorption of the drug, oral ingestible dosage forms of anti-migraine medications have to be administered in large doses of about 20-100 mg. These high doses may causes nausea, vomiting and other unwanted adverse side effects. Many anti-migraine agents are subject to pre-systemic and first pass metabolism. Because of this, it is estimated that as little as 2-10% of the active unchanged drug actually reaches the blood stream. In fact this causes delay in the effectiveness of the drug as a treatment or prophylaxis of the disorder in the patient. Likewise, intranasal administration of anti-migraine agents is hampered with significant limitations due to reduced absorption and low bioavailability.
Injectable and nasal spray forms of anti-migraine agents are also available for the treatment of migraines. Although parenteral administration of anti-migraine agents into the blood stream allows for a lower dose as compared to other non-injectable methods of administration, the inconvenience of an office visit for an injection or problems with the self-administration of injectables are self evident.
In the past, migraine headaches have been treated by use of rizaptriptan, sumatriptan, zolmitriptan or other triptan drugs. These drugs have basically been administered using conventional dosage forms such as pills or capsules or for sumatriptan through injection and nasal spray. The problem with the gastrointestinal (GI) administered triptan anti-migraine pharmaceutical agents is that they have a low GI bioavailability of approximately 15% to 40% and cause GI irritations. In addition, it is important that these drugs be delivered rapidly to a patient to prevent or treat the onset of a migraine headache and give immediate relief. The delay in release of the drug from the dosage form into and the bioavailability of the drug after administration causes undue suffering in the patient which is especially acute with patients suffering from migraine headaches. Therefore, what is needed are formulations that are effective for treating migraines which allow rapid drug release and bioavailability while avoiding the GI irritations which occur with the known administration of anti-migraine medications. Triptans have been developed for the acute treatment of migraine. These medicines are available in the form of tablets for eletriptan, frovatriptan, sumatriptan, zolmitriptan, naratriptan, rizatriptan and almotriptan. These products are intended to be taken in amounts up to a maximum of 5 to 200 mg per day. Table 1 summarizes dosing regimens for triptan products.
TABLE 1Triptan Dosing RegimensMaximum 24 hourGeneric NameDoseBrand NameDoseAlmotriptan12.5mgAxert12.5mgEletriptan40mgRelpax80mgFrovatriptan2.5mgFrova7.5mgNaratriptan2.5mgAmerge5.0mgRizatriptan10mgMaxalt30mgSumatriptan100mgImitrex200mgSumatriptan6mgImitrex6mginjectionSumatriptan nasal20mgImitrex40mgsprayZolmitriptan2.5mgZomig10mgZolmitriptan5mgZomig ZMT10mgZolmitriptan5mgZomig ZMT10mgOral form unless otherwise noted.